1. Field of the Invention
The present invention relates in general to a head-up display system which includes a reflection film onto which light rays carrying images of display information are to be projected from a luminous image source, and more particularly relates to a so-called multicolor head-up display system which includes the reflection film on which a plurality of colors are displayed.
2. Description of the Prior Art
Head-up display systems are already in practical use in aircraft cockpits. Recently efforts have been directed to the development of head-up display systems for automobiles. The systems allow the driver of a car to view a vehicular information of an instrument panel, while looking out a front windshield of the car, by projecting an image of the instrument panel in the direction of the front windshield. For example, JP-B (Patent) 53-38852 discloses a head-up display system in which vehicular speed is displayed by an image of transverse line of which length is a function of the speed.
However, there is a recent demand to display other vehicular informations in addition to vehicular speed in different colors. For this purpose, for example, JP-A (Patent) 60-154226 discloses a so-called multicolor head-up display system which includes a transparent reflection film. A plurality of images of vehicular information are displayed in different colors on the reflection film. The images are projected by projectors onto the reflection film with specific different incident angles, such that each reflected light from the reflection film has a certain specific spectrum and a certain specific color. However, it is difficult or troublesome to finely set the incident lights at certain desired angles so as to obtain desired colors.